Abstract
Viable cell concentration (VCC) is one of the most important process attributes during mammalian cell cultivations. Current state-of-the-art measurements of VCC comprise offline methods which do not allow for continuous process data. According to the FDA’s process analytical technology initiative, process monitoring and control should be applied to gain process understanding and to ensure high product quality. In this work, the use of an inline capacitance probe to monitor online VCCs of a mammalian CHO cell culture process in small-scale bioreactors (250 mL) was investigated. Capacitance sensors using single frequency are increasingly common for biomass monitoring. However, the single-frequency signal corresponds to the cell polarization that represents the viable cell volume. Therefore single-frequency measurements are dependent on cell diameter changes. Measuring the capacitance across various frequencies (frequency scanning) can provide information about the VCC and cope with changing cell diameter. Applying multivariate data analysis on the frequency scanning data successfully enabled direct online monitoring of VCCs in this study. The multivariate model was trained with data from 5 standard cultivations. The model provided a prediction of VCCs with relative errors from 5.5 to 11%, which is a good agreement with the acceptance criterion based on the offline reference method accuracy (approximately 10% relative error) and strongly improved compared with single-frequency results (16 to 23% relative error). Furthermore, robustness trials were conducted to demonstrate the model’s predictive ability under challenging conditions. The process deviations in regard to dilution steps and feed variations were detected immediately in the online prediction of the VCC with relative errors between 6.7 and 13.2%. Thus in summary, the presented method on capacitance frequency scanning demonstrates its suitability for process monitoring and control that can save batches, time, and cost.Graphical abstract
Highlights
Published in the topical collection Advances in Process Analytics and Control Technology with guest editor Christoph Herwig.Electronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.Mammalian cell culture processes for the production of monoclonal antibodies are challenging and complex processes that are crucial in modern medicine to generate pharmaceutical products such as anticancer drugs
To the best of our knowledge, this study presents for the first time a direct datadriven model based on orthogonal partial least squares (OPLS) for Viable cell concentration (VCC) greater than 10 million cells/mL in a fed-batch process
The superiority of frequency scanning over single-frequency measurements was demonstrated, Fig. 7 Batch Evolution Model (BEM) created from all standard cultivation (FB#1–FB#5)
Summary
Pharmaceutical companies face a strong market demand and a high pressure to provide safe products according to quality guidelines and legislations. To improve and sustain high quality in pharmaceutical products, the International Conference on Harmonization (ICH) launched the “Quality by Design” (QbD) initiative within the framework of the ICH Q8 guideline in 2004 [1]. The QbD approach involves, inter alia, the identification of product attributes that are of significant importance to the product’s safety and establishment of robust control strategies to ensure consistent process performance [2]. The initiative focuses on the detection of critical process parameters (CPPs) that have influence on critical quality attributes (CQAs) of the product (e.g., glycosylation profile of a monoclonal antibody). The CPPs should be monitored and controlled online to achieve a constant and high product quality
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